1. Field of the Invention
The present invention relates generally to transcutaneous transfer systems and, more particularly, to a magnetic alignment apparatus for transcutaneous transfer systems.
2. Related Art
The use of implantable medical devices to provide therapy to individuals for various medical conditions has become more widespread as the advantages and benefits such devices provide become more widely appreciated and accepted throughout the population. In particular, devices such as hearing aids, implantable pacemakers, defibrillators, functional electrical stimulation devices such as cochlear prostheses, organ assist or replacement devices, and other medical devices, have been successful in performing life saving and/or lifestyle enhancement functions for a number of individuals.
Medical devices often include one or more sensors, processors, controllers or other functional electrical components that are permanently or temporarily implanted in a patient. Many such implantable devices require power and/or require communications with external systems that are part of or operate in conjunction with the medical device. One common approach to provide for the transcutaneous transfer of power and/or communications with an implantable component is via a transcutaneous transfer system.
One type of medical device that may include a transcutaneous transfer system is a cochlear implant system. Cochlear implant systems provide the benefit of hearing to individuals suffering from severe to profound hearing loss. Hearing loss in such individuals is due to the absence or destruction of the hair cells in the cochlea which transduce acoustic signals into nerve impulses. Cochlear implants essentially simulate the cochlear hair cells by directly delivering electrical stimulation to the auditory nerve fibers. This causes the brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve.
Conventional cochlear implant systems primarily include external components directly or indirectly attached to the body of the patient (sometimes referred to herein as the recipient), and internal components which are implanted in the patient. The external components typically comprise a microphone for detecting sounds, a speech processor that converts the detected sounds into a coded signal, a power source, and an external transmitter antenna coil. The internal components typically comprise an internal receiver antenna coil, a stimulator located within a recess of the temporal bone of the recipient, and an electrode array positioned in the recipient's cochlear.
Collectively, the external transmitter antenna coil and the internal receiver antenna coil form an inductively-coupled coil system of a transcutaneous transfer system. The external transmitter antenna coil is usually positioned on the side of a recipient's head directly facing the implanted antenna coil to allow for the coupling of the coils to enable energy to be transferred from the external to the internal antenna coil. The transfer of energy is controlled to effect the transmission of the coded sound signal and power from the external speech processor to the implanted stimulator unit. Conventionally, the communications link has been in the form of a radio frequency (RF) link, although other such links have been proposed and implemented. Once the coded signal has been transmitted to the implanted receiver antenna coil it is provided to the implanted stimulator unit which processes the coded signal and outputs a stimulation signal to the intra-cochlear electrode assembly which applies the electrical stimulation directly to the auditory nerve of the recipient.
To facilitate the proper alignment of the external transmitter coil and the internal receiver coil, the coils sometimes include a magnet at or near the hub of the coil. The external transmitter coil is held in place and in proper alignment with the implanted antenna coil due to the attraction force of the magnets.